1. Field of the Invention
The present invention relates to a method for converting coordinate values of map data, wherein three-dimensional effects are displayed on a screen by converting X- and Y-axis coordinate values of two-dimensional map data without using a three-dimensional graphic library and an additional storage space.
2. Description of the Related Art
A navigation system detects a current vehicle location using navigation messages transmitted by a plurality of GPS satellites constituting a global position system (GPS) and using detection signals from sensors installed on a vehicle, including a gyro sensor and a speed sensor, and matches the detected current vehicle location to map data so that the current vehicle location can be displayed on a screen. Further, the navigation system provides the functions of searching for a travel path with the shortest distance from the detected current vehicle location to a destination input by a user, a travel path with the shortest travel time based on traffic information, or the like, and guiding the travel of the vehicle along the searched travel path.
In the navigation system, a map around the current vehicle location and the destination should be displayed on the screen in order to display the current vehicle location together with a map on the screen after the matching of the detected current vehicle location to map data or to guide the travel of the vehicle while enabling a user to view the searched travel path of the vehicle from the current vehicle location to the destination.
Upon display of the map on the screen, two-dimensional map data stored in a memory are not displayed on the screen as they are, but converted into three-dimensional map data for a bird's eye view, which in turn are displayed on the screen. This can provide a user with more realistic information on the topography of surrounding regions.
To this end, in a conventional technique, as shown in FIG. 1b, Z-axis is added to two-dimensional map data with X- and Y-axis coordinates shown in FIG. 1a to define a three-dimensional virtual space, and two-dimensional coordinates P(x, y) of each of objects constituting the two-dimensional map data are converted into three-dimensional coordinates P(x, y, z) (the Z-axis coordinate value z is generally set to 0). Then, the entire map data with the converted three-dimensional coordinates are displayed in a state inclined in the same direction on the screen, and three-dimensional objects including buildings are displayed on the three-dimensional map that has been displayed on the screen.
However, since such a conventional technique requires the conversion of two-dimensional map data into three-dimensional map data using an additional three-dimensional graphic library that depends on hardware, the portability of high-level application in an embedded system is low and there is a need for an additional space for storing data to be operated.
Further, when a user views the three-dimensional map that is obtained simply by setting Z-axis coordinate values for respective objects of two-dimensional map data to be converted into three-dimensional map data and simultaneously displaying the three-dimensional map data in the state inclined in the same direction, the user may be more confused as compared with when he/she views a two-dimensional map. That is, in a three-dimensional map, a region close to a view point is displayed on an enlarged scale while a region far away from the view point is displayed on a reduced scale.
However, the conventional technique is to represent three-dimensional effects simply by setting Z-axis coordinate values for objects of two-dimensional map data and displaying the obtained three-dimensional map data in the inclined state. Therefore, since all regions close to and far away from the view point are displayed on the same scale, the user may be confused in correctly determining the position of a certain object displayed on the three-dimensional map.
Moreover, since the conventional technique has a great amount of calculation resulting in a low processing rate and requires an additional space for storing data to be operated, there is a problem in that the technique cannot be applied to mobile equipment such as a mobile communication terminal in which a central processing unit with limited calculation capability is mounted.